Motor-control system.



I w. 0. LUM. I

MOTOR comm SYSTEM. APPLICATION FILED MAR. 30. 1914.

Pate ntd Mar. 14,1916.

Alli-AA 1 lN VENTOR' WITNESSES: 1 4

, UNITE STATES PATENT OFFICE. 1

WALTER o. Linvi, or WILKINSBURG, PENNSYLVA IA, assionon'ro WESTINGHOUSEELECTRIC AND MANUFACTURING COMPANY, A CORPORATION OFI'ENNSYIAVANIA.

MOTOR-CONTROL SYSTEM.

1 '0 add whpm it may] concern: 1 Be it (nown that I, WVALTERO, LnM,acitizen of the United States, and a'resident of Wilkinsln rg. in thecounty of Allegheny and State'ot Pennsylvania, have inventcda new anduseful, Improvement in Motor-Con *trol Systems, of which the followingis a specification My invention relates to motor control sysnection withpi pe-rolling machines and simiconnected in parallel relation, may bealters nately controlled to prevent their operation as generators. I IIn'the operation of pi1')e-rolling, or-pipe straightening machines, andsimilar mecha nisms, the rolls are usually placed at'gjan'.

angle with each other and are provided with separate driving motors, 'Atable comprising a series of rollers provides a support for the pipeduring the process rolling] or straightening. In case the torqueofoneof-the motors exceeds that oithe other, the] corresponding parts,The direction of romatcrial being rolled will be shifted, vertically outof engagement with the rolls; but

if the torque of the other motor isthe greater, the material will belield'in position against thetable. \Vhen the direction of 1'0- tationis reversed, the opposite conditions obtain and the torque oi the firstmentioned motor should be the greater. It is necessary. therefore, topreventthe torque of one oi the motors from exceeding that of the otherwhen the rolls are operated in one direction. and to similarly control.the other motel-when the direction of rotation of the rolls isreversed. 1

I provide a system of control in which one of the driving motors isautonnitic'ally controlled by means of appropriate mechanism to assumeonly a small proportion 'oi the load and also, to prevent it from beingdriven by the other lllOiiUl. as a generator. The motors are thuscontrolled alternately, according to the direction of rotation of therolls oi the machine.

In the accompanying drawing, the single Specification of Letters Patent.implication fiIed March so, 1914. Serial No. 828,206.

Patented Mar. 14, 1916.

figure is a dlagrammatic VIEW of circuits and apparatus embodying myinvention.

Current issupplied from line conductors 1 and 2, which may be. connectedto any suitable source of current, to motors 3 and 4 that are connectedin. parallel relation. The motors 3 and 4 respectively comprisearmatures indicated at 5 and 6 and. shunt field windings 7 and 8. Thedirection of rota- ,tlOIl of the motor 3 is controlled byelectromagnetically operated switches 9, 10, 11 and 12, the'switehes 9and 11 being closed when the motor is to operate in one direction, andthe switches and 12 being closed for rotat on in the reverse direction.A resistor 13,

which is connected .in'series relation withthe armature 5; of the motor3, is adapted to be sliort-c'lrcuited by a switch 1 1 when its actuatingcoil 15 is traversed by a current which .exceeds a predetermined value.

A resistor 16, which is connected in series relation with the fieldwindings 7, is controlled by a switch 17 that is arranged to open whenthe current traversing its actuating coil 18 falls below a predeterminedvaluei The circuits of the motor i are substantially identical withthose of the motor 3 and similar'numerals are employed to designatetation of the motors 3 and 4 is controlled by a controller 19, which,when in one position, causes the actuating, coils 20 and 21 of theswitches 9 and 11 respectively to be energized, and when in a secondposition,

to cause the coils 22 and 23 of the switches the motor 3extends from theline conductor 1 through a conductor 24, switch 9, armature 5, switch11, armature resistor '13, and coil 15to the line conductor 2. Thecircuit of the motor 4 extends from the line conductor 1 through aconductor 25, coil 18, switch 9, armature (3. switch 11, armatureresistor I 13 and coil 15 to the line conductor 2. The

switches 14 will be closed by the respective cells 15 to short circuitthe corresponding ceeds a predeterminedvalue, the switch 17 closed toshort circuit the resistor 16 that is in series with the shunt fieldwinding 8.

\ below a The result is to cause the field of the motor 4 to bestrengthened andthus decrease the armature current. Consequently, themotor 4 develops a torque much less that of the motor 3. Under the mostdesirable operating conditions, sufficient current to prevent it beingdriven as a generator by the motor 3, substantially the entire loadbeing assumed by the motor 3. If the current traversing the coil 18falls predetermined minimum value, the

opens the short-circuit of the resistor 16 to insert'it in series withthe field winding 8 and thus increase the value of the current receivedby the armature 6, .as

switch 1 will be readily understood. The motor 4 is thus prevented fromoperating as a generator by, being caused to develop sufiicient torqueto follow the motor 3. The'switch l7 operates-also to preventthe torqueof the motor 4 from equaling that of the motor 3.

When the controller is moved to its other position, the several switches9 and 11 are allowed to open and the-switches 10 and 12 are closed. Thecoil 18, which controls the switch 17 that is in circuit with the motor4, is rendered inoperative by the opening of the switches 9 and 11. Thecoil 18 that is in circuit with .the by the closing of the switches 10and 12. The operations of the respective motors is the same as before,except that conditions are reversed. The coil 18 that is in circuit withthe armature 5 of the motor 3, operates in the same manner as describedin connection with the motor 4 to automatically control the torque ofthe motor 3.

' It will benoted that I have provided a simple and effective means forautomatically controlling the torque of a motor when it is operated inone direction and for preventing the motor from being driven as agenerator. I have also provided a system inwhich twomotors thuscontrolled are arranged to alternately assume a mechanical loadaccording to the direction of rotation.

I claim as my invention:

1. In a motor control system, the combination with a source of current,and an electric motor, of means dependent upon the value of thecurrentsupplied to said motor for automatically controlling the torque ofrality of electric motors, of means depend- .ent upon the value themotor 4 receives only motor 3, is now energized nation with a, rality ofelectric motors connected thereto,

of the current supplied to the respective motors for automaticallycontrolling the torque of each of said motors, andmeans for controllingthe direction of said motors andfor controlling said automaticcontrolling means. In a motor control system, the combination with asourtie of current, and a plurality of electric motors connected inarallel relation, of means for automatically accelerating each of saidmotors when 'ts armature current falls below. a predetermined value,said means being operative only when the several motors rotate in onedirection.

4. In a motor control system, the combination with a pair of electricmotors connected in parallel relation, of means for automaticallyincreasing the torque of one of said motors whenits armature currentfalls below apredetermined value, when said motor is rotating in onedirection, and means for rendering said automatic means inoperative whenthe motor rotates in the reverse direction.

5. In a motor control system, the combination'with a source of current,and a plurality of motors connected thereto, of means comprising acontroller for controlling the direction of rotation of said motors, andmeans controlled by said controller for automatically controlling thetorque of each of said motors in accordance with the value of thecurrent supplied thereto when the resipective motors rotate in onedirection on y. 1 p

6. In amotor control system, the combination with a source of currentand a pl11.

rality of motors connected thereto, of means respective motor armatures,and means for simultaneously controlling the direction of rotation ofsaid motors and the. circuit conneotlons of sald coils.

In a motor control system, the combi- -nation with a source of current,and an electric motor connected thereto, ofmeans for automaticallycontrolling the torque of said motor when 1ts armature currentfallsbelow a predetermined value, said means comprising a coil incircuit with the motor ar-'.

mature, means comprising a, controller for controlling the direction ofrotation of said motor and for opening cuit of said coil according tothe position of said controller. A

8. In a motor control system,'the combisourceof current, and a pluofmeans for automatically increasing the torque of each of said motorsunder predetermmedclrcuit conditions, and means comprlsingra controllerfor controlling the diand closing the cir-- rection ofrot atioxi of saidmotors, said COQ- subscribed my name this 21st day of ti'ollerogprat'ingg when in one position, to 1914. gender inoperative theautomatic means for if fieontrolling ooe oflsaid motors, and when inWALTER LU 5 lafsecond posltlpn, to render inoperatwe a Witnesses: Isecond automatlocontrollin means. R. T. KINTZING,

In testimony *"y'yhereof, have hereunto B. B. HiNEsi

